Effects of some chelating agents on urinary copper excretion by the rat

The treatment of Wilson's disease, a rare genetic disorder of copper metabolism

Wilson's disease is a rare autosomal recessive disease characterised by the deposition of copper in the brain, liver; cornea, and other organs. The overload of copper inevitably leads to progressive liver and neurological dysfunction. Copper overload in patients with Wilson's disease is caused by impairment to the biliary route for excretion of dietary copper A combination of neurological, psychiatric and hepatic symptoms can make the diagnosis of Wilson's disease challenging. Most symptoms appear in the second and third decades of life. The disease affects between one in 30,000 and one in 100,000 individuals, and is fatal if left untreated. Five drugs are currently available to treat Wilson's disease: British Anti-Lewisite; D-penicillamine; trientine; zinc sulfate or acetate; and ammonium tetrathiomolybdate. Each drug can reduce copper levels and/or transform copper into a metabolically inert and unavailable form in the patient. The discovery and introduction of these five drugs owes more to the inspiration of a few dedicated physicians and agricultural scientists than to the resources of the pharmaceutical industry.

Novel isosteric charge-deficient spermine analogue--1,12-diamino-3,6,9-triazadodecane: synthesis, pK(a) measurement and biological activity

Ionic interactions are essential for the biological functions of the polyamines spermidine and spermine in mammalian physiology. Here, we describe a simple gram scale method to prepare 1,12-diamino-3,6,9-triazadodecane (SpmTrien), an isosteric charge-deficient spermine analogue. The protonation sites of SpmTrien were determined at pH range of 2.2-11.0 using two-dimensional (1)H-(15)N NMR spectroscopy, which proved to be more feasible than conventional methods. The macroscopic pK(a) values of SpmTrien (3.3, 6.3, 8.5, 9.5 and 10.3) are significantly lower than those of 1,12-diamino-4,9-diazadodecane (spermine). The effects of SpmTrien and its parent molecule, 1,8-diamino-3,6-diazaoctane (Trien), on cell growth and polyamine metabolism were investigated in DU145 prostate carcinoma cells. SpmTrien downregulated the biosynthetic enzymes ornithine decarboxylase (ODC) and S-adenosyl-L: -methionine decarboxylase and decreased intracellular polyamine levels, whereas the effects of Trien alone were minor. Interestingly, both SpmTrien and Trien were able to partially overcome growth arrest induced by an ODC inhibitor, alpha-difluoromethylornithine, indicating that they are able to mimic some functions of the natural polyamines. Thus, SpmTrien is a novel tool to influence polyamine interaction sites at the molecular level and offers a new means to study the contribution of the protonation of spermine amino group(s) in the regulation of polyamine-dependent biological processes.

Dendritic poly(L-lysine)-b-Poly(L-lactide)-b-dendritic poly(L-lysine) amphiphilic gene delivery vectors: roles of PLL dendritic generation and enhanced transgene efficacies via termini modification

As an effort to prepare new efficient gene delivery vectors, we have recently developed and reported an amphiphilic dendritic poly(L-lysine)-b-poly(L-lactide)-b-dendritic poly(L-lysine) D(2)-PLLA-D(2) with two-generation PLL dendrons and a PLLA block. In this work, we continued to explore the roles of dendritic PLL generation in DNA binding and intracellular delivery of gene, and a new series of amphiphilic dendritic poly(L-lysine)-b-poly(L-lactide)-b-dendritic poly(L-lysine)s D(n)-PLLA-D(n) (n = 3-5) were synthesized and were structurally characterized. Furthermore, plasmid DNA binding affinity for these cationic amphiphiles was examined by agarose gel electrophoresis and fluorescence titration assay in pure water and PBS buffer solution containing 150 mM NaCl (pH = 7.4), respectively. By dynamic light scattering (DLS) and transmission electronic microscopy (TEM), the interaction and complexation in between were investigated, concerning the DNA/vector polyplex particle morphologies and zeta potentials. Utilizing a human hepatocellular carcinoma cell-line SMMC-7721, cell toxicity, and gene transfection in vitro were explored. To further improve transgene efficiency for these synthetic cationic amphiphiles as gene delivery vectors, new structural DE(n)-PLLA-DE(n) (n = 2-3) were prepared through an amino termini modification of the D(n)-PLLA-D(n) (n = 2-3) with less toxic 4,7,10,13-tetraazatridecanoic acids, and gene transfection with these DE(n)-PLLA-DE(n) (n = 2-3) was examined with an alternative human gastric carcinoma cell-line HGC-27. As a result, the high plasmid DNA binding affinity, low cytotoxicity, and much enhanced transgene efficacy suggest a new possible clue to design effective synthetic gene delivery vectors with amphiphilic skeleton and less toxic polyamine building blocks.

The effect of hexaaza- and hexathia-macrocyclic ligands on transition metal cytotoxicity in human hepatoma-derived cultured cells

The effect of macrocyclic ligands on cytotoxic concentrations of the transition metal ions of copper, zinc, and cadmium was investigated. For this purpose, a hexaaza- [3,6,9,17,20,23-hexaazatricyclo[23.3.1.1(11,15)] triaconta-1(29),11(30),12,14,25,27-hexaene (L2)] and hexathia-chelating ligand [1,4,7,10,13,16-hexathiacyclooctadecane (L3)] were used in the human hepatoma-derived HepG2 cell line. The cytotoxicity was measured by the neutral red uptake inhibition assay. First, the NI50 of the ligands, i.e., the concentration of the ligand inducing a 50% inhibition in neutral red uptake compared to control cells, was determined. In several metal/ligand combination experiments, the effects for L2 were difficult to interpret, whereas for L3 in combination with copper ions, a severe increase -- and for zinc ions, a significant decrease of cell toxicity -- relative to the metal control was observed. To further examine the different effects observed with L3 in combination with, respectively, Cu2+ and Zn2+, the glutathione (GSH) content was measured. The relative GSH content decreased as the concentration of L3 increased. It was proposed that the increased toxicity of the combination Cu(2+)/L3 could be caused by the depletion of GSH and a subsequent inability to scavenge the produced reactive oxygen species (ROS). This hypothesis was supported by experiments during which vitamin E or C was added to the Cu(2+)/L3 system.

Administration of the oral antibiotic frenolicin-B selectively alters copper nutriture in male rats

The polyketide antibiotic Frenolicin-B (FB) produces anorexia and esophageal epithelial hyperplasia (EH) in rats, findings that are characteristic of zinc deficiency. Because FB also chelates divalent cations in vitro, we conducted studies to determine whether FB modifies blood and organ concentrations of zinc and other essential metals (calcium, copper, iron and magnesium). Groups of male Sprague-Dawley rats ( approximately 250g; n = 20/group) consumed diets with adequate (40 microg/g), deficient (<2 microg/g) or fortified (100 microg/g) zinc concentrations ad libitum for 28 d. Two groups fed either Zn-adequate or Zn-fortified diets also were given 100 mg/(kg. d) of FB in diet, and 2 groups were pair-fed controls. Histopathology or metal analyses were performed on tissues from 10 rats/group. FB caused EH of the nonglandular stomach but not of other tissues. Of the metals evaluated, only copper concentrations were significantly reduced in all tissues examined except kidney. A broad range of kidney copper concentrations was found; these concentrations were associated with plasma copper and proteinaceous deposits within tubules. In rats, FB substantially and selectively depletes Cu in vivo, suggesting that drugs with structures that permit metal chelation should be evaluated for their potential to alter trace metal nutriture.

Concurrent administration of D-penicillamine and zinc has no advantages over the use of either single agent on copper excretion in the rat

The present study was conducted to examine in rats whether the combined use of D-penicillamine (DPA) and a zinc salt, or the administration of a DPA/Zn complex could have some advantages over the use of either single agent on the excretion of copper. In a first experiment, three groups of adult male Sprague Dawley rats were given by gavage one of the following treatments for 5 days: 0.5 mmol/kg/day of DPA, 0.046 mmol/kg/day of zinc acetate dihydrate, and 0.5 mmol/kg/day of DPA plus 0.046 mmol/kg/day of zinc acetate dihydrate. A fourth group of rats (control group) received deionized water during the same period. An increase in the urinary excretion of copper was observed following DPA treatment, which continued for at least 5 days after the administration of this compound was stopped. The amount of copper present in the feces, including that in the diet, was approximately 60 times greater than that normally present in control urines. During the period of zinc acetate administration, the amount of copper in the feces was slightly, but significantly greater than that during control, D-penicillamine, or D-penicillamine plus zinc acetate administration. No differences between the treated groups and the control group were found in brain, liver, kidney and spleen concentrations of rats 5 days after the end of the treatment period. In a second experiment, a similar comparison between D-penicillamine and sodium bis(3-mercapto-D-valinato)zinc hexahydrate (Na2[Zn(DPA)2] x 6H2O), both given by gavage, also showed no significant differences in the urinary excretion of copper in rats.

Metabolism of administered triethylene tetramine dihydrochloride in humans

Triethylene tetramine dihydrochloride (trien 2HCl) has been used for the treatment of Wilson's disease, which is characterized by the accumulation of copper in various organs. We previously developed an HPLC system for analyzing trien, and found a trien metabolite in the urine when trien was orally given to humans. In this study, the metabolite was identified as 1-N-acetyltriethylene tetramine (acetyltrien) by FAB-MS and 1H-NMR spectroscopy. Trien and acetyltrien were capable of combining with copper, iron and zinc. However, the chelating activity of acetyltrien was significantly lower than that of trien. When trien was given to healthy adults, the amount of trien excreted in the urine was about 1% of the administered trien, whereas that of acetyltrien was about 8%. Most of the trien was excreted within the first 6 hours after the administration, while acetyltrien was excreted for over 26 hours. The urinary copper, iron and zinc levels all increased in parallel with the trien excretion.